British Postbus Always Rings Twice : Royal Mail vans now take tourists on out-of-way routes serving residents of England, Scotland, Wales.

Like many of her upcountry neighbors, Joan Preston would be stranded on her patch of northwestern England if it weren’t for the postbus.

Every Thursday morning postman Mike Ridge veers off his route and drives his bright red van up the steep hill to Preston’s house, overlooking the lowland pastures of the southern Lake District.

With wheeled shopping cart in tow, the bespectacled Preston clambers through the backdoor and heaves onto one of the van’s benches for the 30-minute trip to Ulverston, where she does her grocery shopping.

“I can’t nip to the corner shop. If we get visitors we can’t say to the kids, ‘Run round to the shop and get a cake,’ ” explained Preston, who has been a regular on the 11-seat postbus since it began on the Ulverston route in June, 1979.

“When it first started it was full. Now people get cars and they don’t bother with the postbus, but they will miss it when it’s gone,” she said to fellow riders Betty Gallo way and Mrs. Saunders on a recent afternoon.

The Royal Mail runs postbus routes in England, Wales and Scotland and has just published two timetables for tourists eager to meander and explore out-of-the-way Britain. One timetable covers the 39 routes in England and Wales, the other includes the 133 Scottish routes.

The first of the buses began in Wales in 1967. Since then they’ve carried grandchildren to reunions on the Farne Islands in the North Sea, milk and bread to shops on the Castle Douglas route in southwest Scotland and pregnant sheep in labor to vets in the Lake District, said Royal Mail spokeswoman Rachel Collinson.

The Ulverston postbus whips along between the hedgerows on the single-lane roads of the Cumbrian foothills, past woods, streams and dales that inspired Wordsworth, Coleridge and the other “Lake Poets.”

Bluebells and dandelions along the road shiver as Ridge rounds a sharp, narrow bend, puffing a cigarette and toot-tooting a warning to cars and sheep.

He says he enjoys the company and will pick up anyone who flags him down.

“If I’m on my own it can get really boring. But if I have company it’s a dawdle,” Ridge said.

In much of rural Britain transportation choices are limited: British Rail long ago abandoned many tiny villages, a commercial bus route is uneconomical and school buses run only twice a day in most places.

“We can take the school bus but it’s very costly and you have to change,” Mrs. Galloway explained.

“Plus the journey times aren’t as convenient,” Mrs. Preston interjected. “Old Bill Neely nearly laid an egg when he had to go on that early morning school bus.”

At Low Wood, outside the village of Haverthwaite, Ridge has half an hour before he can empty the box of its half-dozen letters.

“If I empty it before 5 then someone misses the pickup,” he said. To kill time he visits with Miriam McMahon, who runs the Artcrystal shop.

“It’s not just mail, he’s a real serviceman in the small communities,” McMahon said.

At Grizedale Forest, a schoolboy hops in the back for the one-mile trip home. If he misses the postbus he walks.

“Gordon goes for nothing, he only lives down the road and I don’t know how much I’d charge him anyway,” Ridge said. A round-trip ticket on the 45-mile circuit is about $4.70.

Walkers can alight at Grizedale, where the Forestry Commission runs an information bureau in a stone building.

There are leaflets on walks ranging from the 12-mile Silurian Way to the 1.2-mile Millwood Habitat Trail, which “offers a cross-section of wildlife habitat and is suitable for the elderly and less physically able,” said Forest Officer Peter Brett.

The timetables, which include routes, maps and “places of interest” pictures, are available for free from the Royal Mail, 30 St. James’s Square, London, SW1Y 4PY, England, or at larger post offices and tourist offices like the British Tourist Authority.